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ECG Findings

  • Increased duration (width) of the P wave without affecting its upward amplitude (as commonly seen with right atrial abnormalities)

  • Negative P-wave deflection in lead V1, with width and depth > 40 ms

  • Bifid P wave in lead II with total P duration > 110 ms and > 40 ms between two peaks

  • Notched P wave in II, III, or aVF with duration ≥ 120 ms


  1. Normal P-wave morphology has an amplitude of < 2.5 mV (2.5 vertical boxes) and a duration (width) of <120 ms (three small boxes).

  2. The left atrium depolarizes after the right atrium and therefore has the most effect on the 2nd portion of the P wave.

  3. Causes of left atrial abnormality or P-mitrale include valvular heart disease (mitral and aortic), coronary artery disease, cardiomyopathy, hypertension, and LVH.


Left Atrial Hypertrophy with LVH Present. (ECG contributor: James V. Ritchie, MD.)


The P wave in V1 is downgoing. The downgoing segment is wider and deeper than one small block (double arrows).

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